In many modern tax systems, certain taxes are withheld from a taxpayer's paycheck to satisfy the tax obligations of the taxpayer. Frequently, the amount withheld over a certain period will exceed the amount owed by the taxpayer. The taxpayer is often given an opportunity to claim a refund from the taxing authority. In filing the necessary documents to claim a tax refund, the taxpayer may submit the amount which the taxpayer believes was overpaid. The issuing authority may or may not distribute a refund equal to the amount submitted by the taxpayer. In certain cases, the taxpayer may receive a refund that differs from the taxpayer's expectations. In such cases, the taxpayer may be unable to determine the source of the discrepancy.